Generally, cell processing requires steps in which cells or cell elements are separated from a liquid phase. This separation is typically accomplished by centrifugation. The sterility of the cells being processed is protected by the incorporation of a dynamic seal between rotatable and stationary centrifuge elements, referred to as a “rotating seal”. In addition to deterring the entrance of microbes into the sterile environment of the processing apparatus and the biological materials contained therein, a rotating seal ideally minimizes the leakage of air and frictional heating and is capable of tolerating mild to moderate misalignment and vibration.
A number of designs for rotating seals have been developed. For example, U.S. Pat. No. 3,489,145 by Jodson et al. discloses a lower rotating element that forms a seal with an upper stationary element, and that has a central bore extending throughout. U.S. Pat. Nos. 3,409,203 and 3,565,330 Latham disclose rotating seals formed from a stationary rigid low-friction element in contact with a moving rigid element and an elastomeric element which provides a resilient static seal as well as a modest closing force between the seal surfaces. U.S. Pat. No. 3,801,142 by Jones et al. relates to a pair of elements having confronting annular fluid-tight sealing surfaces maintained in a rotatable but fluid-tight relationship by axial compression of a length of elastic tubing. In the “B. T. Bowl” marketed by Bellco (Mirandola, Italy), a rotating seal is formed between a ceramic ring element attached to rotatable elements of a centrifuge and a fixed graphite ring attached to stationary centrifuge elements; an elastomeric diaphragm is attached at one end to an adapter ring for the graphite ring and at the other end to a stationary part of the centrifuge. U.S. Pat. Nos. 4,300,717 and 5,045,048 by Latham, Jr. relate to a rotating seal which has been modified by the incorporation of recessed areas contiguous with “sealed” regions; the recessed areas are in communication with the external environment and are used to entrap and expel extraneous particles which may form during centrifugation.
In the field of centrifugal cell washing, two technologies currently dominate the state of the art, as exemplified by the Cobe 2991 and the Haemonetics Model 115 cell washers. Both system employ a set of rotating seals to contain the fluids in the disposable rotating containers. These seals have been classified by the FDA as “open” devices for the purpose of washing red blood cells, in that the seals have not yet been validated as having the ability to satisfactorily prevent biological contamination of the sterile interior under all running and handling conditions. According to the American Association of Blood Banks (“AABB”) standards, “when glycerolizing or deglycerolizing involves entering the container, the system is considered ‘open’ and the resulting suspension of deglycerolized cells can be stored for only 24 hours at 1-6 degrees Centigrade.” This 24-hour storage shelf life after deglycerolization, and other factors (including cost), make the foregoing systems less useful for routine inventory management and relegate them primarily to specialty uses such as storing rare blood types, autologous donations, or battlefield applications for the Navy.
None of the foregoing rotating seals provides a seal which permits the storage of processed biological materials such as red blood cells for extended period of time. The foregoing seals do not provide adequate protection from the contamination of processed biological materials by microbial contaminants.